Research finds pirate perch probably use chemical camouflage to fool prey

March 28, 2013
Pirate Perch (Aphredoderus sayanus sayanus). Credit: Ellen Edmonson and Hugh Chrisp

( —It's a nocturnal aquatic predator that will eat anything that fits in its large mouth. Dark and sleek, it hides beneath the water waiting for prey. A Texas Tech University researcher says the target will never know what hit them because they probably can't smell the voracious pirate perch.

After careful investigations, William Resetarits Jr., a professor of biology at Texas Tech, and Christopher A. Binckley, an assistant professor in the Department of Biology at Arcadia University, found that animals normally attuned to predators from their smell didn't seem to detect the pirate perch. It could be the first animal discovered that is capable of generalized chemical that works against a wide variety of prey.

The team published their findings in the peer-reviewed journal The American Naturalist.

Thankfully, at five-and-a-half inches long, only insects, invertebrates, amphibians and other small need worry about the danger hiding near the bottom among the roots and plantlife, Resetarits said.

"We use the term 'camouflage,' because it is readily understandable," he said. "What we really are dealing with is some form of 'chemical deception.' The actual mechanism may be camouflage that makes an organism difficult to detect, that makes an organism difficult to correctly identify, or cloaking where the organism simply does not produce a signal detectable to the receiver."

Resetarits said pirate perch aren't really perch at all, but related to the Amblyopsid cave fish family. Fossils from this fish date back about 24 million years ago.

They make their homes in freshwater ponds and streams in the Eastern United States. Once considered for the aquarium market, the fish got its name because of its penchant for eating all tank mates.

"Pirate perch have some unique aspects to their morphology and life history, but they are generalist predators, and so should have been avoided by like all the other fish tested," he said. "For some reason, they weren't avoided at all."

To test their theory, Resetarits and Binckley ran a series of experiments in artificial pools housing 11 different species of fish, including pirate perch.

The fish were kept at bay at the bottom of the pools with screens so that they could not prey on the beetles and tree frogs that colonized the water.

When it came to choosing a pool, the beetles and frogs consistently steered clear of the water with other fish species in them, most likely because they could smell the presence of fish in the water. However, they had no qualms about moving into pools containing the pirate perch.

"We were incredibly surprised," Resetarits said. "It took a while for us to pull this all together. When we first observed it with tree frogs, we were very surprised and puzzled. But when the same lack of response was shown by aquatic beetles, we were quite literally flabbergasted. We continued to do experiments with other fish and always got the same results. All fish except pirate perch were avoided."

Exactly what the pirate perch is doing to hide isn't yet known, he said. Researchers want to determine how the pirate perch are either scrambling chemical signals or masking their odor. Once they have identified chemical compounds that might explain the behavior, they will return to the field to test with the same tree frogs and beetles as well as other known to respond to fish chemical cues, such as mosquitoes and water fleas.

"We will also test whether this chemical deception works against the pirate perch's own predators," Resetarits said. "Of course, other critical questions that we are working on include just how much advantage in terms of prey acquisition do pirate perch gain as a result of chemical deception. Does this phenomenon occur in closely related species, such as cavefish? Are there prey species that have found a way around the chemical deception? There are many questions now, and I think we have just scratched the surface.

"I think the most important aspect is not the bizarre, just-so story, but the fact that there is no reason to believe that chemical camouflage is less common than visual camouflage. Humans' sense of smell is just not very sophisticated, so we can't simply 'notice' examples of chemical camouflage the way we do visual camouflage. I think chemical camouflage is likely quite common. We are starting pursuit of the larger question, starting with close relatives of pirate perch."

Explore further: Nothing fishy about swimming with same-sized mates

Related Stories

Nothing fishy about swimming with same-sized mates

February 6, 2013

Have you ever wondered why, and how, shoals of fish are comprised of fish of the same size? According to new research by Ashley Ward, from the University of Sydney in Australia, and Suzanne Currie, from Mount Allison University ...

Researchers Find Genes Involved in Yellow Perch Growth

June 14, 2010

( -- Twenty-eight genes that are involved in bulking up yellow perch—an important aquaculture fish in the Great Lakes region—have been discovered by Agricultural Research Service (ARS) scientists and university ...

Salmon can sniff out predators

September 13, 2011

Salmon know when their most common predator is around, because they can tell that it's eaten salmon before, new research shows. Young fish can do this too, even if they've never encountered that particular predator before.

Stealth camouflage at night

March 9, 2007

Cuttlefish are well-known masters of disguise who use highly developed camouflage tactics to blend in almost instantaneously with their surroundings. These relatives of octopuses and squid are part of a class of animals called ...

Finnish record label petition to block Pirate Bay

May 26, 2011

Finnish record labels said Thursday they filed a petition in court to block access to The Pirate Bay, a popular Swedish website that provides access to copyrighted music, movies, and other material.

Recommended for you

The astonishing efficiency of life

November 17, 2017

All life on earth performs computations – and all computations require energy. From single-celled amoeba to multicellular organisms like humans, one of the most basic biological computations common across life is translation: ...

Unexpected finding solves 40-year old cytoskeleton mystery

November 17, 2017

Scientists have been searching for it for decades: the enzyme that cuts the amino acid tyrosine off an important part of the cell's skeleton. Researchers of the Netherlands Cancer Institute have now identified this mystery ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.